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Comparison of maturity based on steroid and vanadyl porphyrin parameters: A new vanadyl porphyrin maturity parameter for higher maturities
Geochimica et Carmochimica .&a Vol. 57, pp. 13?9- I386
Copyrisht 0 1993 PC~@I%XI Press Ltd. Printed in U.S.A.
LETTER
Comparison of maturity based on steroid and vanadyl porphyrin parameters: A new vanadyl porphyrin maturity parameter for higher maturities PADMANABHAN~UNDA~~MAN',*
~~~J.~ICHAELMOL~WAN~
‘ChevronOil FieldResearch Company,PO Box 446, La Habra, CA ~33~, USA zchevron Oil Field ResesrchCompany,W Box 1627,Richmond,CA 90633-0627,USA (ReceivedSeptember 2 1, 1992;accepted in revisedform January 19, 1993 ) Abstract-Correlation are demonstrated between steroidmaturityparameter and the porphyrinmaturity pammeter( PMP) which is based on the ratio of specilic vanadyl porphyrins (V&E/(CzsE + C32D) measured
by HPLC. Measurements from a global selection of > 100 rock extracts and oils show that PMP parallels changes in the Cr&erane 2OS/(2OS -I=20R) and tri/(tri + mono) aromatic steroid ratios, and that all three parameters appear to attain their maximum values at similar maturity levels. The triaromatic steroid side chain cracking parameter, TA I/( I + II), reaches approximately 20% of its maximum value when PMP has reached 100%. These results suggest that PMP is effective in the early to peak portion of the oil window. A new parameter, PMP-2, based on changes in the relative concentrations of two peaks in the HPLC ~nge~~nt (vanadyl “etio” Athens), appears effective in assessing the rnat~~ of source rocks beyond peak oil generation. In ~mbination with PMP this parameter extends the effective range of vanadyl porphyrins parameters to higher maturities as demonstrated by a suite of oils from the Oriente Rasin, Ecuador, South America. INTRODUCTION VANADYL PORPHYRINS UNDERGOcompositional
changes during matumtion mainly due to differential thermal stability of vanadyl “etio” and vanadyl DPEP porphyrins ( BARWISE, 1987 ). These changes can be quantified using the DPEP/ ETIO ratio which decreases with increasing maturity. DPEP/ ET10 is determined by mass spectral analysis of porphyrins isolated from bitumens and oils or by High Performance Liquid ~oma~phy (HPLC) of demetallated porphyrins ( BARWISEet al., 1986). DPEP/ETIO ratio has been used as an indicator of source rock and oil maturity (LOUDA and BAKER,198 1; MACKENZIE et al,, 1980; BARWISEand PARK, 1983; BARWISE,1987). GALLANGO and CASSANI(1992) showed that in very mature samples ET10 porphyrinratios C2sE’/CZ7E’ and C29E/C28E can be used for maturity esti-
expensive instrumentation; (2) ease of analysis; and (3) elimination of the demetallation step. PMP increases fram 0.0 to 1.0 with maturity. Calibrations with other maturity indicators such as Rock-Eval T,,,, ( SUNDARARAMAN et al., 1988 ) and vitriniterefleetanee( SUNDARARAMAN and TEER-
MAN, 1991) show that PMP measures kerogen conversion until peak oil generation where it reaches unity. In this report we examine the correlation between PMP and other commonly used thermal maturity parameters based on steroid biomarkers. A new porphyrin maturity parameter (PMP-2) is described which is based on vanadyl porphyrin species that show changes beyond PMP = 1.00, thereby extending the applicability of vanadyl porphyrins over a wider range of maturity. EXPERIMENTAL
mation of source rocks and oils. This ratio was obtained from the high-performance liquid chromatograms of demetallated porphyrins. The Porphyrin Maturity Parameter (PMP = C2sE/(C2sE + Cs2D)) which measures the changes in the relative pro~~ions of vanadyl C2BEand C&D, where C&E is an “etio” porphyrin with ~enty~i~t carbon atoms and Cs2D is a “DPEP” porphyrin with thirty-two carbon atoms, has been used to estimate the maturity of source rocks and
Samples The Monterey sampies arefromSantaMariaBasin,onshore, California( FETERs et al., 199O),andfroman offshore well,California. The Bakken shaIe samples are from Williston Basin, North Dakota (~NDARA~MAN and RAE~EKE,1993). The Ecuador samples are from Griente Basin, Ecuador (DALY et al., 1991), South America. In addition several samples from the USA, China, New Zealand, Italy, Albania, Yugoslavia, and Cabinda (Africa) were used in this study. General procedures have been previously described for the isolation, purification, and HPLC of vanadyl porphyrins (SUNDARARAMAN, 1985;SUNDARAKAMAN et al., 1988), forhydrous pyrolysis (PETERS et al., 1990), and for the preparation of hydrocarbon fractions (PETERS and MOLDOWAN, 1993 1.
oils (SUNDARARAMAN et al., 1988; AIZENSHTATand SUNDARARAMAN,1990, SLJNDARARAMAN and RAEDEKJZ, 1993 ).
The PMP is calculated matograms of vanadyl method over the mass HPLC of demetallated
using high-performance liquid chroporphyrins. The advantages of this spectral method or the method using porphyrins are the ( 1) relatively in-
kdation, Ikilication, aid
Analysis of Vanadyl Porphyrins
Crude oil or bitumen is chromatographed on an activity II alumina column. Elution with toluene provides a fraction containing saturates and aromatics. Subsequent elution with chloroform yields the polar
* Present address: Chevron Canada, 500 Fifth Ave. SW, Calgary,
Alberta T2P 0L7, Canada.
1379
P. Sundararaman and J. M. Moldowan
I380
fraction containing the metahoporphyrins which is further purified on a propanesulfonic acid bonded silica column. Elution with toluene/ hexane ( 1:I ) removes most of the yellow impurities (polynuclear aromatic compounds). Vanadyl porphyrins are eluted with methylene chloride. The purified vanadyl porphyrin fraction is analyzed using
a 65 cm (25 + 25 + 15) Hypersil Crs column (Shandon Instruments). The solvent mixture consists of 47.5% methanol, 47.5% acetonitrile, and 5% water. The flow rate is 0.8 mL/min and the eluant is monitored using a diode array detector set at 406 nm. RESULTS AND DISCUSSION PMP
versus Steroids
The high-performance liquid chromatograms of vanadyl porphyrins isolated from extracts of Monterey Shale, oKshore,
California, show compositional changes with increasing depth and maturity (Fig. 1a; SUNDARARAMAN, 1992 ). During early to peak stages of maturation the concentration of Cz8E increases relative to that of&D (samples 6990’ - 7880’; Figure la). These changes can be expressed in terms of the ratio CzsE/(CzsE + C32D) or PMP. PMP data for eighty-six oils and thirty-four source rock extracts from several countries (USA, Ecuador, New Zealand, China, Cabin&, Italy, Albania, Yugoslavia) were compared with biomarker maturity parameters [Czs-sterane isomerization ratio (2OS/( 20s + 20R)), monoaromatic steroid aromatization ratio ( CzsTA/ (CzBTA + &MA)), and the triaromatic steroid side chain cracking parameter (TA (I/I + II))] for the same suite of
C28E I
C28E I
C28E LMWE
11
0
30
40
50
60
70
80
0.2
0.4
0.6
0.6
1
90
Time (mini
FIG.1.(a)High-performance liquid chromatograms of vanadyl porphyrins extracted from a Monterey source rock of increasing maturity from a single well, offshore, California. (b) PMP and PMP-2 plotted against depth. (PMP = Cr8E/(C2rE + Cr2D); PMP-2 = LMWE/( LMWE +&SE)). PMP = 0.25 indicatesonset ofhydrocarbon generation. LMWE stands for Low Molecular Weight Etio porphyrin. The maximum possible value of I.0 for PMP-2 was not reached in this well. Error in the measurements of PMP and PMP-2 is r0.02 (2%).
A new vanadyl porphyria maturity parameter
samples (Fig. 2 ), Previous studies indicate that PMP = 0.25 corresponds to the onset of oil generation. MACKENZIE ( 1984) and PETERSand MQWOWAN( 1993) illustrated and discussed the effective ranges of biomarker maturity parameters vs. vitrinite reflectance and oil generation. In the data set of tbis study, the C&erane isomerization ratio rangea from about 0.3 to a maximum 0.54 in rock extracts that are well within the oil window (with one exceptional point at 0.60) and in oils in good agreement with previous work (0.56 maximum, SEIFERT and MOLDOWAN, 1986). Maximum values suggest that a sample has experienced, at mi~mum, a level of matu~tion near peak oil generation and no mrther increase in the ratio is expected at higher maturities. (Although, recent work suggests possible reversals to lower isomerization values at higher maturities; PETERS et al., 1990; MARZ~and RULLK~T~ER,1992; REQUEJO,1992.) These and previous data (Fig. 2a and SUNDARARAMAN et al., 1988, respectively) indicate that whereas C29_steraneisomerization values range from about 0.3 to 0.56 in the early to peak oil window, PMP values range from about 0.25 to 1.0. Thus, the CrsE/(CrsE + Cs*D) ratio undergoes 75% of its change and therefore should be well suited to gauge maturity changesin this range.
1381
The PMP also shows an increasing trend with increases in the monoaromatic steroid aromatization parameter (Fig. 2b). The aromatization parameter covers a range of about 0.6 to 1.0 in the early to peak oil window, again, vs. about 0.25 to 1.O for PMP. Thus, PMP displays nearly twice the range of change in this maturity range. There is also a systematic change in the triaromatic steroid side chain cracking parameter in this maturity range. However, in these samples it ranges from about 0.05 to 0.2 while PMP ranges from 0.25 to 1.0 (Fig. 2~). Much of the range for the cracking parameter occurs at maturities higher than peak generation. Judging from Fig. 3.46 in PEG and MOLDOWAN ( f993), the cracking parameter may reach a value somewhat higher than 0.2 but less than 0.6 at peak generation. Thus, it is markedly more useful in assessment of maturity above peak generation than any of the other parameters discussed here. Vanadyl Porphyrins Beyond Peak 011 Generation The HPLC peaks representing CrrE and &D used to measure PMP change markedly from 6990’ to 7880’ in the Monterey source rock sequence (Fig. 1), but additional dif-
(a) 0.6
1
f
I
I
I
1.0
+
8 H
08
8
0.6
z z $
0.4
1 I
/
I ?
I
0.0
0.2
I
0.4
0.6
I
0.8
PMP
0.6 c
I I
I I
I I
I I
I I
PrG.2. PMPplotted against (a) 2OS/(2OS+ 2OR)CB Sterane,(r = 0.62), (b) Tri/(Tri + Mono) aromatic steroids, and (c) TA I/( I+ II) (r = 0.89) for numerous oils and source rock extracts. PMP = 0.25 indicates onset of hydrocarbon generation based on PMP. The line in (b) shows the trend and does not have any statistical significance.
I
1.0
1382
P. Sundararaman and J. ht. Moldowan
ference5 are observed in the porphyrin
~~butio~ below 7880’. At mom advanced stages of maturation (7880’~86 10’; Fig. la) changes occur in the relative concentrations of the early eluting porphyrins. Based on HPLC retention times these peaks appear to represent lower molecular weight “etio” porphyrins. One peak labeled LMWE (Low Molecular Weight Etio) shows a prominent increase with depth relative to Cr8E (Fig. 1). Comparable changes can be reproduced in the laboratory by pyrolysing an immature Monterey phosphatic source rock at different temperatures (Fig. 3; SUNDARARAMAN, 1992). This change in the compositions of vanadyl porphyrins at higher maturity (Fig. 1) and higher pyrolysis temperatures (Fig. 3) can be represented by the parameter, PMP-2 = LMWE I( LMWF + C&E).
Comparison of PMP and PMP-2 (F&. 4) shows that during the early stages of maturation {between PMP of 0.0 and 0.8) PMP increases, but there is little change in PMP-2. At advanced stages of maturation (beyond PMP of 0.8 ) there is little change in PMP, whereas there is a large change in PMP2. Thus, combined use of PMP and PMI-2 extends the utility of vanadyl porphyrins for estimating source rock maturity beyond peak oil generation. Application
to Matnrity
Evaiuation of Oils
An application of PMP-2 is dernon~~ with a set of oils from the Oriente Basin, Ecuador (Table 1; Fig. 5; DALY et al., 199 I). These oils have undergone different degrees of
C28E I
ILMWE 0
30
40
50
60
70
80
0.2
0.4
0.6
0.0
1
so
Time lminl
FIG. 3. (a) High-performance liquid chromatograms of vanadyl porphyrins extracted from an immature Monterey source rock pyrolysed at different temperatures for 72 h. (b) PMP and PMP-2 plotted against pyrolysis temperatures. PMP = QsE/(CzsE + &D); PMP-2 = LMWE/(LMWE + C=E). PMP = 0.25 indicates onset of hydrocarbon generation based on PMP. LMWE stands for Low Molecuktr Weight Etio porphyrin. Error in the measurements of PMP and PMP-2 is +0.02 ( 2%) .
A newwnadyl porphyrinmaturity
1383
parameter
Hydrous Pyrolysis,MontereyShale, California
I
I
I
0.4
0.6
0.6
1.0
PMP-2
RG. 4. Cross plot of PMP vs. PMP-2 showing little change in PMP-2 until PhlrP reaches a value of 0.9. Beyond this PMP shows little change, whereas there is a large change in PMP-2. Error in the measurementsof PMP and PMP-2 is *0.02 (2%).
biodegradation and their relative maturities cannot be determ&d using conventional parameters such as API gravity and % sulfur ( BASKIN and PETERS, 1992). Some biomarker maturity parameters (described in detail in PETJXS and MOLDOWAN, 1993) for these oils are listed and defined in
Table 1. In many of the oils, the &,-stemne 2OS/(2OS + 20R) and the cw&3/(a/@ + W(Y) ratios are near their equilibrium values (about 0.56 and 0.70, respectively, Table 1). Therefore, the sterane parameters are of limited use in differentiating the maturity of these oils. The aromatization pa-
Table 1. Geochemical data for the oils from Oriente Basin, Ecuador.
Tiiuino - 1
10565-10626
25.8
1.26
Tiiuino - 1
10312-10370
16.0
1.96
0.51
0.67
0.93
0.19
0.91
0.24
0.69
0.16
TiiUkO ” 1
9736-9766
14.8
2.47
0.46
0.48
0.92
0.14
0.74
0.11
Maranacu- 1
9147.9180
15.7
1.56
0.62
0.66
0.96
0.14
0.93
0.22
&shin, - 1
6068-6521
14.7
1.99
0.47
0.59
0.67
0.15
0.57
0.14
14.9
3.02
0.46
0.57
0.66
0.12
0.39
0.12
9799-9017
31.5
0.46
0.63
0.70
0.87
0.23
0.93
0.31
LqeAgrb-1
9945-10110
27.7
0.60
0.96
0.44
LagoAgrb-t
9696-10102
27.6
0.66
0.51
0.68
0.68
0.22
0.96
0.43
Saoha-3
9935-9962
25.6
0.92
0.92
0.24
Sacha-
9730.9756
26.2
0.92
0.51
0.67
0.91
0.13
0.93
0.25
9040-9070
25.6
0.84
0.52
0.65
0.90
0.12
0.92
0.23
0.61
0.63
0.66
0.66
0.17
OS3
0.27
Ogian - I Laoa Agrb-1
Shushufindi- 1 Grit0
1 Data lrom motastawareactbn monitoring(MRM) GCMS W&Q mh 400 -+ 217 transitbnson a VG Mkmmass7070H mass spuummetw. Greek lettersindkate weochsmktry of Ii atom6 at 5.14 snd 17 fwitkns, rotpectively,in 24-athykhohastans.205 and 20R referto aau stwaodmmistry. * Data fromcrebct6dbn monitoring usingmh 231 br tdwomatk (TA) stero&Bwd m/z 253 for monoaromatk(MA) atomids.CaTA indudes209 end 2OR. C&&A 5p(CH#OS. @se, Peters and hloldowm,l&s). TA I- C, + C2,.TA II- C, + Cn + C,, 2Wand2OR. !nciudea 6a{&fOR, 6c@fpS, sa(H)20Ft.5@(HpOS,~(W#OA,
1384
P. Sundararaman and J. M. Moldowan
INDEX MAP
8 Cononaco
aTIGUINQ-3
_
l NASHINQ-1
San Jacinto Y
PERU
FIG. 5. Map showing the location of the oil samples from Ecuador used in this study.
C&TA/( CzsTA + (&MA ) is also ineffbctive because many of the values are similar and approach the maximum value of 1.0 (Table 1). The aromatic steroid side chain cracking parameter TA I/( I + II) ranges between 0.12 and 0.23 and is not approaching its end value ( 1.O). Therefore, the TA I/( I + II) parameter offers the best potential among the listed conventional biomarker parameters for maturity ranking this oil set. PMP values show that Oglan- 1, Nashino-1, and Tiguino1 (Table 1) are less mature than the rest of the oils, but do not vary sufhciently to differentiate the rest of the oils. On rameter
the other hand, PMP-2 can be used to rank these oils of
increasing maturity. Parallels exist between TA I/(1 + II) and the porphyrin maturity parameters but the correlation is not perfect. One potential problem is that TA I/(X + II) can show strong facies dependence ( MOLD~WAN et al., 1986). Neither PMP nor PMP-2 show any facies dependency (DAHL et al., 1993; P. Sundararaman, unpubl. data). Nevertheless, the highest values for both TA I/(1 -t II) and PMP-2 are found in the Lago Agrio oils indicating that they are the most mature. Based on PMP and PMP-2 (Fig. 6) the oils are ranked in increasing order of maturity: Oglan < Nashino < Tiguino,
A new vanadyl porphyrin maturity parameter
1385 0
orito
0
Shushufindi-1
0
Sacha-
(9730-9756)
X
Sacha-
(9935-9982)
+
Lago Agrio-1 (9898-l 0102)
A
Lago Agrio-I
0
Lago Agrio-1 (9799-9817)
n
Oglan-1
0
Maranacu-1
A
Tiguino-I
(9738-9786)
0
Tiguino-I
(10312-l
q
Tiguino-I
(10585-l 0620)
q
Nashino-1
(9040-9070)
(9945-l 0110)
(9147-9180) 0370)
(6058-6521)
PMP-2 FIG. 6. PMP plotted against PMP-2 for a set of oils from Oriente Basin, Ecuador.
9738 < Tiguino, 103 12 < Maranacu = Shushutindi = Sacha, 9935 = Sacha, 9730 = Tiguino, 10585 < Orito c Lago Agrio, 9799 < Lago Agrio, 9945 = Lago Agrio, 9898. Limitations of PMP and PMP-2 Vanadyl porphyrins are typically abundant in the extracts of Type II kerogens. Hence, PMP and PMP-2 are excellent parameters for estimating the maturity of marine source rocks. In marine rocks, vitrinite reflectance is often of limited use because vitrinite is commonly low or absent. There are some limits to the use of porphyrins. Since coals and source rocks deposited in a deltaic environment do not contain vanadyl porphyrins, PMP and PMP-2 cannot be used to estimate the maturity of these rocks or oils derived from them. Because these two parameters are measured on vanadyl porphyrins, the technique cannot be used if only Ni-porphyrins are present. CONCLUSIONS PMP is useful in estimating the maturity of source rocks and oils at less than peak oil generation. It reaches a maximum value ( 1.OO) close to peak oil generation, similar to the CZssterane isomerization [2OS/( 20s + 20R) w 0.561 and monoaromatic steroid aromatization [ CzsTA /( C=TA + t&MA) = 1.01 parameters. However, its wider range of values in the early to peak oil window suggests that it may be a more sensitive maturity indicator than the parameters based on steroids for this maturity range. A new maturity parameter PMP-2, based on the changes in two peaks in the HPLC, LMWE and CZaE, can be used to estimate maturities of source rocks beyond peak oil generation. Comparison of PMP and PMP-2 shows that PMP increases during the early
stages of maturation. At later stages of maturation there is little change in PMP, whereas there is a large change in PMP2. The utility of PMP-2 in ranking oil maturity is demonstrated using a set of oils from the Oriente Basin, Ecuador. The change in PMP-2 with maturity could be due to differential stability of LMWE and t&E porphyrins. Acknowledgments-We thank Chevron Overseas Petroleum Inc. and Petroecuador for the oils from Ecuador, Mr. J. J. Jaime for the porphyrin analysis, Ms. M. M. Pefia and Ms. C. Y. Lee for the biomarker analysis and Mr. R. F. Dias and Dr. K. E. Peters for the hydrous pyrolysis experiments. We also thank Chevron Oil Field Rematch Company and Chevron Overseas Petroleum Inc. for giving us permission to publish this work and our colleagues for helpful discussion. We are grateful to S. C. Brassell, M. Fowler, A. J. G. Barwise and an unidentified reviewer for their comments on the manuscript. Editorial handling: G. Faure REFERENCES AIZENSHTATZ. and SUNDARARAMAN P. ( 1990) Maturation trend in oils and asphalts of the Jordan Rift: Utilization of detailed vanadylporphyrin analysis. Geochim. Cosmochim. Acta. 53, 31853188. BARWISEA. J. G. (1987) Mechanism involved in altering Deoxophylloerythroetioporphyrin-Etioporphyrin ratios in sediments and oils. In Metal Complexes in Fossil Fuels, Geochemistry, Characterization andProcessing(ed. R. H. FILBYand J. F. BRANTHAVEN); ACS Symposium Series 344, pp. IOO-109. BARVV~SE A. J. G. and PARKP. J. D. ( 1983) Petroporphyrin fingerprinting as a geochemical marker. In Advances in Organic Geechemistry 1981 (ed. M. BJORC~Y), pp. 668-674. Wiley. BARWISEA. J. G., EVER~HEDR. P., WOLFG. A., and MAXWELL J. R. ( 1986) High-Performance liquid chromatographic analysis of free-base porphyrins: I. An improved method. J. Chromatogr. 368, l-9. BASKIND. K. and PETERSK. E. ( 1992) Early generation characteristics of a sulfur-rich Monterey kerogen. AAPG Bull. 76, I - 13.
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P. Sundararamanand J. M. Moldowan
DAHL J., MOLDOWANJ. M., and S~NDA~~MAN P. ( 1993) Relationshipof biomarkerdistributionto depositionsIenvironment: PhosphoriaFormation,Montana, USA Org. Geochem.(in press). DALY A. R., MARRO W. E., ~CHOELKO!=F N. B., and MOLDOWAN J. M. ( 199 I ) Hydrocarbonsystem in the forelrmd basin and sub
Andean zone of Ecuador. In 4th Simposia Bolivariano, Bogota, Columbia (abstr.) . GALLANGO0. and CASSANIF. ( 1992) Biological marker maturity parameters of marine crude oils and rock extracts from the Maraca&o Basin, Venezuela. Org. Geochem. 18,2 1S-224. LOUDAJ. W. and BAKERE. W. ( 1981) Geochemistry of tetmpyrrole, carotenoid and perylene pigments in sediments from the San Miguel Gap (Site 467) and Baja Cahfomia borderland (Site 471), Deep Sea Drilling Project, Leg 63. In init. Reports ofthe Deep Sea frilling ~oj~-~IIZ, pp. 785-818. US Govt. Printing O&e. MACKENZIEA. S. (1984) Application of biological markers in petroleum geochemistry. In Advances in Petrolarm Geochemistry (ed. J. BnoOKSand D. H. WELTE), p. 115-2 14. Academic Press. MACKENWEA. S., QUIRKEJ. M. E., and MAXWELL J. R. ( 1980) Molecular parameters of maturation in the Toarcian Shales, Paris Basin, France-II: Evolution of metrdloporphyrins.In Advances in Organic Geochemistry 1979 (ed. A. G. DOLJcLASand J. R. MAXWELL), pp. 239-248. Pergamon Press. MARZI R. and RULLK~TTER J. ( 1992) Qualitative and quantitative evolution and kinetics of biological marker tmnsformations-laboratory experiments and application to the Michigan Basin. In BioiogicxdMarkers in Sediments and Petroleum (ed. J. M. MOLDOWAN, P. ALIBRECHT, and R. P. PHILP), pp. 18-41. Prentice Hall. MOLD~WANJ. M., SUNDA~RAMANP., and S~HOELLM. ( 1986) Sensitivityof biomarkerpropertiesto depositionalenvironment
and for source input in the Lower Toamian of SW~~ny.
Org.
Gee&em. M, 9 15-926. PETERSK. E. and MOLDOWANJ. M. ( 1993)
The Biomarker Guide. Prentice-Hall. PETERSK. E., MOLUUWAN J. M., and SUNDARARAMAN P. ( 1990) Effects of hydrous pyrolysis on biomarker thermal maturity parameters: Monterey Phosphatic and Siliceous members. Org. Geothem. 15,249-265. REQUEJO A. G. ( 1992) Quantitative analysis of triterpane and smrane biomarkem:Methodology and applicationsin molecularmaturity parameters.In Biological Markers in Sediments and Petroleum fed. J. M. MOLDOWANet rd.), pp. 222-240. Prentice-Hall.
SEIFERTW. K. and MOLWWANJ. M. f 1986) Use of biological markers in petroleum exploration. In Meth~ in Ge~bemist~ and Geophysics (ed. R. B. JOHNS), p. 261-290. SUNDA~~~AN P. ( 1985) Hi~-~~o~an~ liquid chromatography of van~yl~~h~ns. Anal. Chem. 57,2204-2206. SUNDARARAMAN P. ( 1992) Comparison of natural and artificial maturation of vanadyl porphyrins. In Biofogicai Markers in Sediments and Petroleum (ed. J. M. MOLDOWAN et ah), pp. 3133 19. Prentice-I&ill. SUNDARARAMAN P. and RAEDEKJZ L. D. ( 1993) Vanadyl porphyrins in exploration: Maturity indicators of source rocks and oils. Appl. Geochem. (in press). SUNDARARAMAN P. and TEERMANS. C. ( 199I ) Porphyrins in extracts as indicators of maturity and depositional environment of Tertiary source rocks from Central Sumatra. In 19th Ann. Indon. Petrof Assoc. C&v. (Jakarta. indon. I. Vol. 1.DD.62 l-635. SUNDA~~MAN P., B~GGSWi R., R&otDs’J.G., and FETZER J. C. ( 1988) Vanadyl~~h~~, indicators of kerogen breakdown and generation of petroleum. Ge~him. Cos~him. Acta 52, 2337-2341.
Copyrisht 0 1993 PC~@I%XI Press Ltd. Printed in U.S.A.
LETTER
Comparison of maturity based on steroid and vanadyl porphyrin parameters: A new vanadyl porphyrin maturity parameter for higher maturities PADMANABHAN~UNDA~~MAN',*
~~~J.~ICHAELMOL~WAN~
‘ChevronOil FieldResearch Company,PO Box 446, La Habra, CA ~33~, USA zchevron Oil Field ResesrchCompany,W Box 1627,Richmond,CA 90633-0627,USA (ReceivedSeptember 2 1, 1992;accepted in revisedform January 19, 1993 ) Abstract-Correlation are demonstrated between steroidmaturityparameter and the porphyrinmaturity pammeter( PMP) which is based on the ratio of specilic vanadyl porphyrins (V&E/(CzsE + C32D) measured
by HPLC. Measurements from a global selection of > 100 rock extracts and oils show that PMP parallels changes in the Cr&erane 2OS/(2OS -I=20R) and tri/(tri + mono) aromatic steroid ratios, and that all three parameters appear to attain their maximum values at similar maturity levels. The triaromatic steroid side chain cracking parameter, TA I/( I + II), reaches approximately 20% of its maximum value when PMP has reached 100%. These results suggest that PMP is effective in the early to peak portion of the oil window. A new parameter, PMP-2, based on changes in the relative concentrations of two peaks in the HPLC ~nge~~nt (vanadyl “etio” Athens), appears effective in assessing the rnat~~ of source rocks beyond peak oil generation. In ~mbination with PMP this parameter extends the effective range of vanadyl porphyrins parameters to higher maturities as demonstrated by a suite of oils from the Oriente Rasin, Ecuador, South America. INTRODUCTION VANADYL PORPHYRINS UNDERGOcompositional
changes during matumtion mainly due to differential thermal stability of vanadyl “etio” and vanadyl DPEP porphyrins ( BARWISE, 1987 ). These changes can be quantified using the DPEP/ ETIO ratio which decreases with increasing maturity. DPEP/ ET10 is determined by mass spectral analysis of porphyrins isolated from bitumens and oils or by High Performance Liquid ~oma~phy (HPLC) of demetallated porphyrins ( BARWISEet al., 1986). DPEP/ETIO ratio has been used as an indicator of source rock and oil maturity (LOUDA and BAKER,198 1; MACKENZIE et al,, 1980; BARWISEand PARK, 1983; BARWISE,1987). GALLANGO and CASSANI(1992) showed that in very mature samples ET10 porphyrinratios C2sE’/CZ7E’ and C29E/C28E can be used for maturity esti-
expensive instrumentation; (2) ease of analysis; and (3) elimination of the demetallation step. PMP increases fram 0.0 to 1.0 with maturity. Calibrations with other maturity indicators such as Rock-Eval T,,,, ( SUNDARARAMAN et al., 1988 ) and vitriniterefleetanee( SUNDARARAMAN and TEER-
MAN, 1991) show that PMP measures kerogen conversion until peak oil generation where it reaches unity. In this report we examine the correlation between PMP and other commonly used thermal maturity parameters based on steroid biomarkers. A new porphyrin maturity parameter (PMP-2) is described which is based on vanadyl porphyrin species that show changes beyond PMP = 1.00, thereby extending the applicability of vanadyl porphyrins over a wider range of maturity. EXPERIMENTAL
mation of source rocks and oils. This ratio was obtained from the high-performance liquid chromatograms of demetallated porphyrins. The Porphyrin Maturity Parameter (PMP = C2sE/(C2sE + Cs2D)) which measures the changes in the relative pro~~ions of vanadyl C2BEand C&D, where C&E is an “etio” porphyrin with ~enty~i~t carbon atoms and Cs2D is a “DPEP” porphyrin with thirty-two carbon atoms, has been used to estimate the maturity of source rocks and
Samples The Monterey sampies arefromSantaMariaBasin,onshore, California( FETERs et al., 199O),andfroman offshore well,California. The Bakken shaIe samples are from Williston Basin, North Dakota (~NDARA~MAN and RAE~EKE,1993). The Ecuador samples are from Griente Basin, Ecuador (DALY et al., 1991), South America. In addition several samples from the USA, China, New Zealand, Italy, Albania, Yugoslavia, and Cabinda (Africa) were used in this study. General procedures have been previously described for the isolation, purification, and HPLC of vanadyl porphyrins (SUNDARARAMAN, 1985;SUNDARAKAMAN et al., 1988), forhydrous pyrolysis (PETERS et al., 1990), and for the preparation of hydrocarbon fractions (PETERS and MOLDOWAN, 1993 1.
oils (SUNDARARAMAN et al., 1988; AIZENSHTATand SUNDARARAMAN,1990, SLJNDARARAMAN and RAEDEKJZ, 1993 ).
The PMP is calculated matograms of vanadyl method over the mass HPLC of demetallated
using high-performance liquid chroporphyrins. The advantages of this spectral method or the method using porphyrins are the ( 1) relatively in-
kdation, Ikilication, aid
Analysis of Vanadyl Porphyrins
Crude oil or bitumen is chromatographed on an activity II alumina column. Elution with toluene provides a fraction containing saturates and aromatics. Subsequent elution with chloroform yields the polar
* Present address: Chevron Canada, 500 Fifth Ave. SW, Calgary,
Alberta T2P 0L7, Canada.
1379
P. Sundararaman and J. M. Moldowan
I380
fraction containing the metahoporphyrins which is further purified on a propanesulfonic acid bonded silica column. Elution with toluene/ hexane ( 1:I ) removes most of the yellow impurities (polynuclear aromatic compounds). Vanadyl porphyrins are eluted with methylene chloride. The purified vanadyl porphyrin fraction is analyzed using
a 65 cm (25 + 25 + 15) Hypersil Crs column (Shandon Instruments). The solvent mixture consists of 47.5% methanol, 47.5% acetonitrile, and 5% water. The flow rate is 0.8 mL/min and the eluant is monitored using a diode array detector set at 406 nm. RESULTS AND DISCUSSION PMP
versus Steroids
The high-performance liquid chromatograms of vanadyl porphyrins isolated from extracts of Monterey Shale, oKshore,
California, show compositional changes with increasing depth and maturity (Fig. 1a; SUNDARARAMAN, 1992 ). During early to peak stages of maturation the concentration of Cz8E increases relative to that of&D (samples 6990’ - 7880’; Figure la). These changes can be expressed in terms of the ratio CzsE/(CzsE + C32D) or PMP. PMP data for eighty-six oils and thirty-four source rock extracts from several countries (USA, Ecuador, New Zealand, China, Cabin&, Italy, Albania, Yugoslavia) were compared with biomarker maturity parameters [Czs-sterane isomerization ratio (2OS/( 20s + 20R)), monoaromatic steroid aromatization ratio ( CzsTA/ (CzBTA + &MA)), and the triaromatic steroid side chain cracking parameter (TA (I/I + II))] for the same suite of
C28E I
C28E I
C28E LMWE
11
0
30
40
50
60
70
80
0.2
0.4
0.6
0.6
1
90
Time (mini
FIG.1.(a)High-performance liquid chromatograms of vanadyl porphyrins extracted from a Monterey source rock of increasing maturity from a single well, offshore, California. (b) PMP and PMP-2 plotted against depth. (PMP = Cr8E/(C2rE + Cr2D); PMP-2 = LMWE/( LMWE +&SE)). PMP = 0.25 indicatesonset ofhydrocarbon generation. LMWE stands for Low Molecular Weight Etio porphyrin. The maximum possible value of I.0 for PMP-2 was not reached in this well. Error in the measurements of PMP and PMP-2 is r0.02 (2%).
A new vanadyl porphyria maturity parameter
samples (Fig. 2 ), Previous studies indicate that PMP = 0.25 corresponds to the onset of oil generation. MACKENZIE ( 1984) and PETERSand MQWOWAN( 1993) illustrated and discussed the effective ranges of biomarker maturity parameters vs. vitrinite reflectance and oil generation. In the data set of tbis study, the C&erane isomerization ratio rangea from about 0.3 to a maximum 0.54 in rock extracts that are well within the oil window (with one exceptional point at 0.60) and in oils in good agreement with previous work (0.56 maximum, SEIFERT and MOLDOWAN, 1986). Maximum values suggest that a sample has experienced, at mi~mum, a level of matu~tion near peak oil generation and no mrther increase in the ratio is expected at higher maturities. (Although, recent work suggests possible reversals to lower isomerization values at higher maturities; PETERS et al., 1990; MARZ~and RULLK~T~ER,1992; REQUEJO,1992.) These and previous data (Fig. 2a and SUNDARARAMAN et al., 1988, respectively) indicate that whereas C29_steraneisomerization values range from about 0.3 to 0.56 in the early to peak oil window, PMP values range from about 0.25 to 1.0. Thus, the CrsE/(CrsE + Cs*D) ratio undergoes 75% of its change and therefore should be well suited to gauge maturity changesin this range.
1381
The PMP also shows an increasing trend with increases in the monoaromatic steroid aromatization parameter (Fig. 2b). The aromatization parameter covers a range of about 0.6 to 1.0 in the early to peak oil window, again, vs. about 0.25 to 1.O for PMP. Thus, PMP displays nearly twice the range of change in this maturity range. There is also a systematic change in the triaromatic steroid side chain cracking parameter in this maturity range. However, in these samples it ranges from about 0.05 to 0.2 while PMP ranges from 0.25 to 1.0 (Fig. 2~). Much of the range for the cracking parameter occurs at maturities higher than peak generation. Judging from Fig. 3.46 in PEG and MOLDOWAN ( f993), the cracking parameter may reach a value somewhat higher than 0.2 but less than 0.6 at peak generation. Thus, it is markedly more useful in assessment of maturity above peak generation than any of the other parameters discussed here. Vanadyl Porphyrins Beyond Peak 011 Generation The HPLC peaks representing CrrE and &D used to measure PMP change markedly from 6990’ to 7880’ in the Monterey source rock sequence (Fig. 1), but additional dif-
(a) 0.6
1
f
I
I
I
1.0
+
8 H
08
8
0.6
z z $
0.4
1 I
/
I ?
I
0.0
0.2
I
0.4
0.6
I
0.8
PMP
0.6 c
I I
I I
I I
I I
I I
PrG.2. PMPplotted against (a) 2OS/(2OS+ 2OR)CB Sterane,(r = 0.62), (b) Tri/(Tri + Mono) aromatic steroids, and (c) TA I/( I+ II) (r = 0.89) for numerous oils and source rock extracts. PMP = 0.25 indicates onset of hydrocarbon generation based on PMP. The line in (b) shows the trend and does not have any statistical significance.
I
1.0
1382
P. Sundararaman and J. ht. Moldowan
ference5 are observed in the porphyrin
~~butio~ below 7880’. At mom advanced stages of maturation (7880’~86 10’; Fig. la) changes occur in the relative concentrations of the early eluting porphyrins. Based on HPLC retention times these peaks appear to represent lower molecular weight “etio” porphyrins. One peak labeled LMWE (Low Molecular Weight Etio) shows a prominent increase with depth relative to Cr8E (Fig. 1). Comparable changes can be reproduced in the laboratory by pyrolysing an immature Monterey phosphatic source rock at different temperatures (Fig. 3; SUNDARARAMAN, 1992). This change in the compositions of vanadyl porphyrins at higher maturity (Fig. 1) and higher pyrolysis temperatures (Fig. 3) can be represented by the parameter, PMP-2 = LMWE I( LMWF + C&E).
Comparison of PMP and PMP-2 (F&. 4) shows that during the early stages of maturation {between PMP of 0.0 and 0.8) PMP increases, but there is little change in PMP-2. At advanced stages of maturation (beyond PMP of 0.8 ) there is little change in PMP, whereas there is a large change in PMP2. Thus, combined use of PMP and PMI-2 extends the utility of vanadyl porphyrins for estimating source rock maturity beyond peak oil generation. Application
to Matnrity
Evaiuation of Oils
An application of PMP-2 is dernon~~ with a set of oils from the Oriente Basin, Ecuador (Table 1; Fig. 5; DALY et al., 199 I). These oils have undergone different degrees of
C28E I
ILMWE 0
30
40
50
60
70
80
0.2
0.4
0.6
0.0
1
so
Time lminl
FIG. 3. (a) High-performance liquid chromatograms of vanadyl porphyrins extracted from an immature Monterey source rock pyrolysed at different temperatures for 72 h. (b) PMP and PMP-2 plotted against pyrolysis temperatures. PMP = QsE/(CzsE + &D); PMP-2 = LMWE/(LMWE + C=E). PMP = 0.25 indicates onset of hydrocarbon generation based on PMP. LMWE stands for Low Molecuktr Weight Etio porphyrin. Error in the measurements of PMP and PMP-2 is +0.02 ( 2%) .
A newwnadyl porphyrinmaturity
1383
parameter
Hydrous Pyrolysis,MontereyShale, California
I
I
I
0.4
0.6
0.6
1.0
PMP-2
RG. 4. Cross plot of PMP vs. PMP-2 showing little change in PMP-2 until PhlrP reaches a value of 0.9. Beyond this PMP shows little change, whereas there is a large change in PMP-2. Error in the measurementsof PMP and PMP-2 is *0.02 (2%).
biodegradation and their relative maturities cannot be determ&d using conventional parameters such as API gravity and % sulfur ( BASKIN and PETERS, 1992). Some biomarker maturity parameters (described in detail in PETJXS and MOLDOWAN, 1993) for these oils are listed and defined in
Table 1. In many of the oils, the &,-stemne 2OS/(2OS + 20R) and the cw&3/(a/@ + W(Y) ratios are near their equilibrium values (about 0.56 and 0.70, respectively, Table 1). Therefore, the sterane parameters are of limited use in differentiating the maturity of these oils. The aromatization pa-
Table 1. Geochemical data for the oils from Oriente Basin, Ecuador.
Tiiuino - 1
10565-10626
25.8
1.26
Tiiuino - 1
10312-10370
16.0
1.96
0.51
0.67
0.93
0.19
0.91
0.24
0.69
0.16
TiiUkO ” 1
9736-9766
14.8
2.47
0.46
0.48
0.92
0.14
0.74
0.11
Maranacu- 1
9147.9180
15.7
1.56
0.62
0.66
0.96
0.14
0.93
0.22
&shin, - 1
6068-6521
14.7
1.99
0.47
0.59
0.67
0.15
0.57
0.14
14.9
3.02
0.46
0.57
0.66
0.12
0.39
0.12
9799-9017
31.5
0.46
0.63
0.70
0.87
0.23
0.93
0.31
LqeAgrb-1
9945-10110
27.7
0.60
0.96
0.44
LagoAgrb-t
9696-10102
27.6
0.66
0.51
0.68
0.68
0.22
0.96
0.43
Saoha-3
9935-9962
25.6
0.92
0.92
0.24
Sacha-
9730.9756
26.2
0.92
0.51
0.67
0.91
0.13
0.93
0.25
9040-9070
25.6
0.84
0.52
0.65
0.90
0.12
0.92
0.23
0.61
0.63
0.66
0.66
0.17
OS3
0.27
Ogian - I Laoa Agrb-1
Shushufindi- 1 Grit0
1 Data lrom motastawareactbn monitoring(MRM) GCMS W&Q mh 400 -+ 217 transitbnson a VG Mkmmass7070H mass spuummetw. Greek lettersindkate weochsmktry of Ii atom6 at 5.14 snd 17 fwitkns, rotpectively,in 24-athykhohastans.205 and 20R referto aau stwaodmmistry. * Data fromcrebct6dbn monitoring usingmh 231 br tdwomatk (TA) stero&Bwd m/z 253 for monoaromatk(MA) atomids.CaTA indudes209 end 2OR. C&&A 5p(CH#OS. @se, Peters and hloldowm,l&s). TA I- C, + C2,.TA II- C, + Cn + C,, 2Wand2OR. !nciudea 6a{&fOR, 6c@fpS, sa(H)20Ft.5@(HpOS,~(W#OA,
1384
P. Sundararaman and J. M. Moldowan
INDEX MAP
8 Cononaco
aTIGUINQ-3
_
l NASHINQ-1
San Jacinto Y
PERU
FIG. 5. Map showing the location of the oil samples from Ecuador used in this study.
C&TA/( CzsTA + (&MA ) is also ineffbctive because many of the values are similar and approach the maximum value of 1.0 (Table 1). The aromatic steroid side chain cracking parameter TA I/( I + II) ranges between 0.12 and 0.23 and is not approaching its end value ( 1.O). Therefore, the TA I/( I + II) parameter offers the best potential among the listed conventional biomarker parameters for maturity ranking this oil set. PMP values show that Oglan- 1, Nashino-1, and Tiguino1 (Table 1) are less mature than the rest of the oils, but do not vary sufhciently to differentiate the rest of the oils. On rameter
the other hand, PMP-2 can be used to rank these oils of
increasing maturity. Parallels exist between TA I/(1 + II) and the porphyrin maturity parameters but the correlation is not perfect. One potential problem is that TA I/(X + II) can show strong facies dependence ( MOLD~WAN et al., 1986). Neither PMP nor PMP-2 show any facies dependency (DAHL et al., 1993; P. Sundararaman, unpubl. data). Nevertheless, the highest values for both TA I/(1 -t II) and PMP-2 are found in the Lago Agrio oils indicating that they are the most mature. Based on PMP and PMP-2 (Fig. 6) the oils are ranked in increasing order of maturity: Oglan < Nashino < Tiguino,
A new vanadyl porphyrin maturity parameter
1385 0
orito
0
Shushufindi-1
0
Sacha-
(9730-9756)
X
Sacha-
(9935-9982)
+
Lago Agrio-1 (9898-l 0102)
A
Lago Agrio-I
0
Lago Agrio-1 (9799-9817)
n
Oglan-1
0
Maranacu-1
A
Tiguino-I
(9738-9786)
0
Tiguino-I
(10312-l
q
Tiguino-I
(10585-l 0620)
q
Nashino-1
(9040-9070)
(9945-l 0110)
(9147-9180) 0370)
(6058-6521)
PMP-2 FIG. 6. PMP plotted against PMP-2 for a set of oils from Oriente Basin, Ecuador.
9738 < Tiguino, 103 12 < Maranacu = Shushutindi = Sacha, 9935 = Sacha, 9730 = Tiguino, 10585 < Orito c Lago Agrio, 9799 < Lago Agrio, 9945 = Lago Agrio, 9898. Limitations of PMP and PMP-2 Vanadyl porphyrins are typically abundant in the extracts of Type II kerogens. Hence, PMP and PMP-2 are excellent parameters for estimating the maturity of marine source rocks. In marine rocks, vitrinite reflectance is often of limited use because vitrinite is commonly low or absent. There are some limits to the use of porphyrins. Since coals and source rocks deposited in a deltaic environment do not contain vanadyl porphyrins, PMP and PMP-2 cannot be used to estimate the maturity of these rocks or oils derived from them. Because these two parameters are measured on vanadyl porphyrins, the technique cannot be used if only Ni-porphyrins are present. CONCLUSIONS PMP is useful in estimating the maturity of source rocks and oils at less than peak oil generation. It reaches a maximum value ( 1.OO) close to peak oil generation, similar to the CZssterane isomerization [2OS/( 20s + 20R) w 0.561 and monoaromatic steroid aromatization [ CzsTA /( C=TA + t&MA) = 1.01 parameters. However, its wider range of values in the early to peak oil window suggests that it may be a more sensitive maturity indicator than the parameters based on steroids for this maturity range. A new maturity parameter PMP-2, based on the changes in two peaks in the HPLC, LMWE and CZaE, can be used to estimate maturities of source rocks beyond peak oil generation. Comparison of PMP and PMP-2 shows that PMP increases during the early
stages of maturation. At later stages of maturation there is little change in PMP, whereas there is a large change in PMP2. The utility of PMP-2 in ranking oil maturity is demonstrated using a set of oils from the Oriente Basin, Ecuador. The change in PMP-2 with maturity could be due to differential stability of LMWE and t&E porphyrins. Acknowledgments-We thank Chevron Overseas Petroleum Inc. and Petroecuador for the oils from Ecuador, Mr. J. J. Jaime for the porphyrin analysis, Ms. M. M. Pefia and Ms. C. Y. Lee for the biomarker analysis and Mr. R. F. Dias and Dr. K. E. Peters for the hydrous pyrolysis experiments. We also thank Chevron Oil Field Rematch Company and Chevron Overseas Petroleum Inc. for giving us permission to publish this work and our colleagues for helpful discussion. We are grateful to S. C. Brassell, M. Fowler, A. J. G. Barwise and an unidentified reviewer for their comments on the manuscript. Editorial handling: G. Faure REFERENCES AIZENSHTATZ. and SUNDARARAMAN P. ( 1990) Maturation trend in oils and asphalts of the Jordan Rift: Utilization of detailed vanadylporphyrin analysis. Geochim. Cosmochim. Acta. 53, 31853188. BARWISEA. J. G. (1987) Mechanism involved in altering Deoxophylloerythroetioporphyrin-Etioporphyrin ratios in sediments and oils. In Metal Complexes in Fossil Fuels, Geochemistry, Characterization andProcessing(ed. R. H. FILBYand J. F. BRANTHAVEN); ACS Symposium Series 344, pp. IOO-109. BARVV~SE A. J. G. and PARKP. J. D. ( 1983) Petroporphyrin fingerprinting as a geochemical marker. In Advances in Organic Geechemistry 1981 (ed. M. BJORC~Y), pp. 668-674. Wiley. BARWISEA. J. G., EVER~HEDR. P., WOLFG. A., and MAXWELL J. R. ( 1986) High-Performance liquid chromatographic analysis of free-base porphyrins: I. An improved method. J. Chromatogr. 368, l-9. BASKIND. K. and PETERSK. E. ( 1992) Early generation characteristics of a sulfur-rich Monterey kerogen. AAPG Bull. 76, I - 13.
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P. Sundararamanand J. M. Moldowan
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Andean zone of Ecuador. In 4th Simposia Bolivariano, Bogota, Columbia (abstr.) . GALLANGO0. and CASSANIF. ( 1992) Biological marker maturity parameters of marine crude oils and rock extracts from the Maraca&o Basin, Venezuela. Org. Geochem. 18,2 1S-224. LOUDAJ. W. and BAKERE. W. ( 1981) Geochemistry of tetmpyrrole, carotenoid and perylene pigments in sediments from the San Miguel Gap (Site 467) and Baja Cahfomia borderland (Site 471), Deep Sea Drilling Project, Leg 63. In init. Reports ofthe Deep Sea frilling ~oj~-~IIZ, pp. 785-818. US Govt. Printing O&e. MACKENZIEA. S. (1984) Application of biological markers in petroleum geochemistry. In Advances in Petrolarm Geochemistry (ed. J. BnoOKSand D. H. WELTE), p. 115-2 14. Academic Press. MACKENWEA. S., QUIRKEJ. M. E., and MAXWELL J. R. ( 1980) Molecular parameters of maturation in the Toarcian Shales, Paris Basin, France-II: Evolution of metrdloporphyrins.In Advances in Organic Geochemistry 1979 (ed. A. G. DOLJcLASand J. R. MAXWELL), pp. 239-248. Pergamon Press. MARZI R. and RULLK~TTER J. ( 1992) Qualitative and quantitative evolution and kinetics of biological marker tmnsformations-laboratory experiments and application to the Michigan Basin. In BioiogicxdMarkers in Sediments and Petroleum (ed. J. M. MOLDOWAN, P. ALIBRECHT, and R. P. PHILP), pp. 18-41. Prentice Hall. MOLD~WANJ. M., SUNDA~RAMANP., and S~HOELLM. ( 1986) Sensitivityof biomarkerpropertiesto depositionalenvironment
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SEIFERTW. K. and MOLWWANJ. M. f 1986) Use of biological markers in petroleum exploration. In Meth~ in Ge~bemist~ and Geophysics (ed. R. B. JOHNS), p. 261-290. SUNDA~~~AN P. ( 1985) Hi~-~~o~an~ liquid chromatography of van~yl~~h~ns. Anal. Chem. 57,2204-2206. SUNDARARAMAN P. ( 1992) Comparison of natural and artificial maturation of vanadyl porphyrins. In Biofogicai Markers in Sediments and Petroleum (ed. J. M. MOLDOWAN et ah), pp. 3133 19. Prentice-I&ill. SUNDARARAMAN P. and RAEDEKJZ L. D. ( 1993) Vanadyl porphyrins in exploration: Maturity indicators of source rocks and oils. Appl. Geochem. (in press). SUNDARARAMAN P. and TEERMANS. C. ( 199I ) Porphyrins in extracts as indicators of maturity and depositional environment of Tertiary source rocks from Central Sumatra. In 19th Ann. Indon. Petrof Assoc. C&v. (Jakarta. indon. I. Vol. 1.DD.62 l-635. SUNDA~~MAN P., B~GGSWi R., R&otDs’J.G., and FETZER J. C. ( 1988) Vanadyl~~h~~, indicators of kerogen breakdown and generation of petroleum. Ge~him. Cos~him. Acta 52, 2337-2341.